In computer systems, a file system maintains a namespace that contains all of the filenames of files that it manages. When an application needs to perform an input/output (IO) operation on a file, it accesses the file from storage by specifying the filename contained in the namespace that is associated with the file.
In a distributed file system where different computer systems access files that are stored in central storage, a namespace map provides a mapping from a computer system's local namespace to the namespace that is maintained for files in the central storage. For example, a file area network (FAN), also known as network attached storage virtualization, file switch, and network file management, is a storage virtualization solution that sits logically between applications and the central storage and virtualizes the application's perspective of storage. With this arrangement, FAN can be used to centrally manage data.
A virtualization aware file system, known as Ventana, extends a conventional distributed file system to virtual machine environments. Ventana combines the sharing benefits of a distributed file system with versioning, access control, and disconnected operation features that are available with virtual disks. A detailed description of Ventana is provided in a publication from Stanford University, Department of Computer Science, authored by Ben Pfaff, et al. The publication is entitled “Virtualization Aware File Systems: Getting Beyond the Limitations of Virtual Disks.”